Fluid-solid coexistence from two-phase simulations: Binary colloidal mixtures and square well systems

摘要

Molecular dynamics simulations are performed to clarify the reasons for the disagreement found in a previous publication [G. A. Chapela, F. del Rio, and J. Alejandre, J. Chem. Phys. 138(5), 054507 (2013)] regarding the metastability of liquid-vapor coexistence on equimolar charged binary mixtures of fluids interacting with a soft Yukawa potential with kappa sigma = 6. The fluid-solid separation obtained with the two-phase simulation method is found to be in agreement with previous works based on free energy calculations [A. Fortini, A.-P. Hynninen, and M. Dijkstra, J. Chem. Phys. 125, 094502 (2006)] only when the CsCl structure of the solid is used. It is shown that when pressure is increased at constant temperature, the solids are amorphous having different structures, densities, and the diagonal components of the pressure tensor are not equal. A stable low density fluid-solid phase separation is not observed for temperatures above the liquid-vapor critical point. In addition, Monte Carlo and discontinuous molecular dynamics simulations are performed on the square well model of range 1.15 sigma. A stable fluid-solid transition is observed above the vapor-liquid critical temperature only when the solid has a face centered cubic crystalline structure. (C) 2015 AIP Publishing LLC.